Thanks everyone for perspectives offered in the C7 and C8 A6 Allroad Forums last month in respect of my next purchase decision (C7 vs C8); your 'hand-holding' was very useful.
In the event, I went for another low mileage 2018 C7 with a confirmed 26K on the clock, but which came with a full tech package and a few more HP (now 268, rather than 214), and having had the old one's Adblue system faults fixed by a main dealer (-fitting new pump etc) I'm now about to unload it, albeit with its very obvious persistent oil and coolant leaks unsorted, for which I'll naturally take a hit, no doubt, with 130K on clock. These include oil leaks around the sump's retaining bolts, recurrent leakage from the front crankshaft seal (previously replaced x2 this year) as well as from the cylinder head gaskets.
Having had the oil and coolant leaks investigated by an 'Audi Specialist', they feel sure that their present widespread distribution and recurrence speak to an underlying raised crank-case pressure as a cause. There were also surprised by the vehicle's history of having needed no less than 5/6 diesel injectors reseated with new retaining bolts and seals, (including several retaining bolts' cylinder-head sockets' heli-coiled) in the last couple of years, their being unable to recall a 3.0L TDi in any VAG vehicle which has exhibited this problem. But what amazed them more was how smoothly the car runs and, in respect of poke and economy, I cannot fault it myself either.
Potential causes of raised crank-case pressure obviously include include piston ring leaks and crank-case vent problems. However, I cannot believe, given the feel-good stuff above, that the underlying issue is leaking piston rings. Furthermore, in respect of blocked venting, I had one cracked (plastic) rocker cover replaced last year, and the other, and its integral vent, rechecked and declared OK just last month.
Reading round the subject of the occurrence of raised crank-case pressure in the VAG 3.0L TDI on line, I'm afraid I've drawn a blank in respect of this as a common or inevitable problem. Any ideas as to its likely cause would therefore be gratefully received. The Audi Specialist indicted the blow-back around the car's previously loose diesel injectors, but I didn't completely follow the physics. Obviously, with another (2018) A6 C7 3.0L TDI on my hands now, I'd like to do everything possible to mitigate the risks of further problems of this nature as the 'new' A6 C7 Allroad ages. I'm also inclined to take out an AUDI extended warranty.
Thank you.
In the event, I went for another low mileage 2018 C7 with a confirmed 26K on the clock, but which came with a full tech package and a few more HP (now 268, rather than 214), and having had the old one's Adblue system faults fixed by a main dealer (-fitting new pump etc) I'm now about to unload it, albeit with its very obvious persistent oil and coolant leaks unsorted, for which I'll naturally take a hit, no doubt, with 130K on clock. These include oil leaks around the sump's retaining bolts, recurrent leakage from the front crankshaft seal (previously replaced x2 this year) as well as from the cylinder head gaskets.
Having had the oil and coolant leaks investigated by an 'Audi Specialist', they feel sure that their present widespread distribution and recurrence speak to an underlying raised crank-case pressure as a cause. There were also surprised by the vehicle's history of having needed no less than 5/6 diesel injectors reseated with new retaining bolts and seals, (including several retaining bolts' cylinder-head sockets' heli-coiled) in the last couple of years, their being unable to recall a 3.0L TDi in any VAG vehicle which has exhibited this problem. But what amazed them more was how smoothly the car runs and, in respect of poke and economy, I cannot fault it myself either.
Potential causes of raised crank-case pressure obviously include include piston ring leaks and crank-case vent problems. However, I cannot believe, given the feel-good stuff above, that the underlying issue is leaking piston rings. Furthermore, in respect of blocked venting, I had one cracked (plastic) rocker cover replaced last year, and the other, and its integral vent, rechecked and declared OK just last month.
Reading round the subject of the occurrence of raised crank-case pressure in the VAG 3.0L TDI on line, I'm afraid I've drawn a blank in respect of this as a common or inevitable problem. Any ideas as to its likely cause would therefore be gratefully received. The Audi Specialist indicted the blow-back around the car's previously loose diesel injectors, but I didn't completely follow the physics. Obviously, with another (2018) A6 C7 3.0L TDI on my hands now, I'd like to do everything possible to mitigate the risks of further problems of this nature as the 'new' A6 C7 Allroad ages. I'm also inclined to take out an AUDI extended warranty.
Thank you.
